Bmac,
One of the things I like about you is your ability to plan and your attention to detail. It's evident in your home that your building, and I got this feeling it will be in your trails as well.
An added benifit to hogging the saplings is no cleanup. All the material is turned to mulch!!! After hauling branches to the burn pile, you'll really appreciate this.
All the trails I made started with a pass or two with the tractor and bush hog on the back. My favorite method is to just find a thin spot in the saplings and run them down. I keep this up until I break something, or I get to the other side. Then I go over it a few more times trying to make it wider and either straighter or a more natural curve.
The little stumps and spikes left from mowing will rot away in time, and until they do, they usually don't present much of a hazard to ATV tires. Buy some slime and an air compresor. You'll end up with flats anyway, and slime works really well at keeping it to a minimum. Every one of my tires have slime in them, and it's a one time deal. Drive until you get a flat, fill with slime and wait until the next tire goes flat and repeat the process. hahahaha
Your fear of a chainsaw is well founded. They terify me as well. Everytime I use one, I think of all the things that could happen and how bad it's gonna hurt. Hopefully this fear keeps me cautious and it never happens.
Nothing will cut the trees like a chainsaw. Sawzalls are fine for cutting a limb here or there, but it's kind of silly to think you'll clear a decent sized trail with one.
In my opinion, that trail should be at least twice as wide as the four wheeler with three times the width being even better.
Chainsaws come in all sorts of sizes. One of my favorites is a little one on the end of a 12 foot pole that I use for cutting branches way up that I can't reach. It cuts right through the branches nice and fast.
For a starter chainsaw, I'd think a small one would be ideal for what you want to do. Something in the 12 inch bar range, or less. Just big enough to cut the limbs and small tree's you'll be dealing with. It will be very light and easy to control.
Just about everyone who sells chainsaws has the little ones. Just read through the brand discussions if that's important, othewise, buy from the closest supplier that your comfortable with.
You really suprised me with your reluctance to buy a trailer. I think this is a huge mistake on your part. Granted, you might not use if every day, or even once a month, but you will use it several times a year, and it will become one of those things you wont' be able to live without.
It's not just for hauling your tractor. I rarely use mine for that. How about culverts, pipe, lumber, furniture, ATV's, vehicles, plywood and just about anything else. The longer bed and lower platform make it easier to load than a pickup bed. Since you can disconnect it, you don't have to unload it right away either. I've left stuff on mine for weeks at a time to keep other areas clear that I was working on.
Look at 16 foot ones with duel axles. Mine was $900 brand new. Prices are usually pretty competitive, but do some research and compare before you buy. Like anything, some are better than others.
Good luck,
Eddie